This invention relates to a new use of certain substances in mammals. More specifically, it relates to the use of cyclic guanosine 3xe2x80x2, 5xe2x80x2-monophosphate phosphodiesterase type five (cGMP PDE V) inhibitors to increase fecundity in mammals.
There is a constant need, in the husbandry of food animals, to increase economic efficiency. One way of achieving this is by increasing the efficiency of the breeding process by, for instance, increasing the chances of a viable pregnancy occurring, increasing the number of offspring per pregnancy and reducing the mortality of young animals. The mortality rate of young animals, particularly piglets, is known to be related, in part, to their birth weight since below a certain birth weight threshold, mortality rates increase dramatically. Hence agents that increase birth weight by, for instance, promoting foetal growth, reducing or overcoming intrauterine growth retardation or normalising intrauterine growth and/or prolonging or normalising of threatened gestation periods, will tend to reduce the mortality of young animals. Further, agents which promote the growth of oocytes, zygotes, blastocysts or embryos or increase the rate of survival of embryos or foetuses will tend to increase the chances of a viable pregnancy occurring and the number of offspring per pregnancy. Establishing viable pregnancy in dairy cattle is especially important since pregnancy is a prerequisite for lactation to occur. The fertility of dairy cattle has been declining for some time, at the rate of about 1% per annum.
Such agents as described above would be expected to also have obvious applications in companion animals such as cats, dogs and horses, and in human health. Miscarriage and pre-term labour account for significant foetal loss in pregnancy and low birthweight and associated conditions contribute to significant perinatal morbidity and mortality. Also there is increasing evidence that low birth weight in relation to gestational age not only increases the immediate danger to the foetus, but also the incidence of cardiovascular disease, such as carotid stenosis, in later life. Hence agents which promote the growth of oocytes, zygotes, blastocysts, embryos or foetuses, increase the rate of survival of embryos or foetuses or increase the birth weight of a progeny would be useful in the management certain problems in human reproduction.